[Schuyler113]

So for the past year or so I have been getting intermittent misfires / hesitations on my n54 335i. I recently got it walnut blasted, given it was over 100k and had never had it done by the previous owner or myself.

However, the misfires continue. I was previously getting a code for LPF sensor (29F3), that continued to persist after replacing the sensor. Though I did not use an oem sensor, so I suppose there is a chance I got a lemon. I have since replaced it with a OEM new style sensor and line, and the code seems to have gone away and the sensor is reading.

The car seems to cruise well, but it will occasionally have a hesitation or slight misfire (once every few minutes). At WOT, it is much more of a problem. The hesitations are more significant. Sometimes it's a quick bump and the car continues to pull, sometimes the misfires continue, and then throws a code and runs very rough until you restart the car (cylinder de-activated?). I have only done this once though.

The car seems to run pretty lean in boost at low/mid RPM (14ish:1 until ~5k rpm, then it leans out to upper 12s)



Actions taken so far (problem existed before everything except the first line):
HPFP / Turbos / index 12 injectors replaced ~50k ago
Just walnut blasted intake
Just replaced LPFPS.
Just replaced spark plugs
Just reset adaptions
Just checked compression (all good)

Modifications:
Dual Cone Intake
Catless Downpipes
JB4 (currently running Map0)

I have included several logs below.

Things I've noticed:
Coolant temp at times seems to randomly drop 50-100deg, then jump back up.
Certain ignition coils seem to do the same thing at times, dropping 20+ degrees (often on only a single coil)

3 Logs where I attempt to capture the hesitations (log ended immediately after occurrence)
https://datazap.me/u/schuyler/7-6-20...k-hesitation-1
https://datazap.me/u/schuyler/7-6-20...k-hesitation-2
https://datazap.me/u/schuyler/7-6-20...k-hesitation-3

3rd Gear Pull (end of log)
https://datazap.me/u/schuyler/7-5-2018-home-work

Any help would be greatly appreciated. I'm officially stumped.

[dcafs]

Did you ever get a coolant temp plausibility code 2EE3?

[JuniorB]

Why no coils? Is it misfire with codes, or just misses?

[Blown95ImpalaSS]

What active codes do you have via jb4? Have you replaced coils too?

[Schuyler113]

Originally Posted by Blown95ImpalaSS

What active codes do you have via jb4? Have you replaced coils too?

Originally Posted by JuniorB

Why no coils? Is it misfire with codes, or just misses?

Originally Posted by dcafs

Did you ever get a coolant temp plausibility code 2EE3?

No active codes (aside from downpipes).

Hadn't replaced the coils just due to everything I'd read pointing me towards those throwing a code. It is definitely something I could try though.

[Nexus313]

Change your coils (Use high quality non CHINA stuff... Same with spark plugs/ any other parts)
Check your PRE-CAT O2 sensors. (CHANGE to OEM Bosch Sensors only!)
Try cleaning vanos solenoids (Easy, quick)
Are you on OEM cats? What I'm seeing more common nowadays is that when you run a car too long on misfires, the unburnt fuel clogs up the cats.. This makes the car run rough, and the oil temps get hot quickly and fluctuate alot. Typically the codes for this is 29F4/29F5.. There was a guy on here who tested his Pre-cats with a DIY backpressure gauge.


Edit: Saw that you have downpipes.. I would check them out.

Here's the thread: https://www.e90post.com/forums/showt...t=clogged+cats

[Schuyler113]

Originally Posted by Nexus313

Change your coils (Use high quality non CHINA stuff... Same with spark plugs/ any other parts)
Check your PRE-CAT O2 sensors. (CHANGE to OEM Bosch Sensors only!)
Try cleaning vanos solenoids (Easy, quick)
Are you on OEM cats? What I'm seeing more common nowadays is that when you run a car too long on misfires, the unburnt fuel clogs up the cats.. This makes the car run rough, and the oil temps get hot quickly and fluctuate alot. Typically the codes for this is 29F4/29F5.. There was a guy on here who tested his Pre-cats with a DIY backpressure gauge.


Edit: Saw that you have downpipes.. I would check them out.

Here's the thread: https://www.e90post.com/forums/showt...t=clogged+cats

My car has always taken (what seems like) a very long time for the oil to heat up, but that is definitely something I can check out. I obviously don't have primary cats due to taking out the oem downpipes, but I could definitely try and check the secondary cats.

I've stopped driving the car, as one cylinder appears to have signs of detonation. I replaced the coil in that cylinder, and am still getting misfires. Still not throwing any codes other than 29F4 and 29F5 (which I believe are due to the catless downpipes).

Cold starts are fine, so I'm very hesitant to assume one of my 50k old index 12s has gone bad. I have the engine bay apart at the moment though, so I am planning to pull the other spark plugs to inspect, and pull the cyl3 injector to see if the end shows the darkened signs of leaking.

Pics of the sparkplug in question (and codes):